HAN, D.W.; WATSON, R.D.*: Cell signaling pathways for ecdysteroidogenesis in blue crab Y-organs

Crustacean Y-organs secrete ecdysteroid molting hormones. The production of ecdysteroids by Y-organs is regulated (negatively) by a neuropeptide, molt-inhibiting hormone (MIH). Available data indicate the suppressive effect of MIH on ecdysteroidogenesis is mediated by a rise in the intracellular level of one or more cyclic nucleotide second messengers (cAMP, cGMP, or both). We report here the results of experiments conducted in vitro to assess the possible roles of these key second messengers in cell signaling pathways for ecdysteroidogenesis in Y-organs of the blue crab, Callinectes sapidus. Cholera toxin, an activator of Gs-protein, had no effect on ecdysteroid secretion by Y-organs in vitro. Likewise, addition of dibutryl cAMP (10 mM) or 8-bromo-cAMP (10 mM) to Y-organ incubations had no effect on ecdysteroid secretion. By contrast, addition of 8-bromo-cGMP to Y-organ incubations significantly suppressed ecdysteroid secretion. We are currently conducting experiments designed to test the hypothesis that the effect of MIH on ecdysteroidogenesis in blue crab Y-organs is mediated by a cGMP second messenger. Supported by MS/AL Sea Grant and the UAB Graduate School.